Ocular hypertension (OH) is defined as a condition where the intraocular pressure is elevated above normal range but where there is no evidence of glaucomatous damage to the optic disc or to the visual field and where the chamber angle is open. The incidence of OH is about 10% of the population and about 10 times greater than that of open angle glaucoma. Although certain risk factors are known it is not possible to identify those hypertensives who are at risk for developing glaucomatous lesions. A group of subjects with ocular hypertension will be followed for 5 years in a prospective study. In addition to normal clinical examination special methods will be used: Aqueous humor dynamics: Constant pressure tonography; a carbonic anhydrase inhibitor test; Fundus: stereochronoscopy; analysis of the nerve fiber layer. Visual functions: Kinetic and static perimetry; color vision test with the chromagraph; contrast sensitivity test. The purpose is to see whether these new methods can improve the power to predict the occurrence of early glaucomatous damage and detect glaucomatous lesions when they still are in a reversible stage.